{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,21]],"date-time":"2026-09-21T17:01:49Z","timestamp":1790010109876,"version":"4.0.1"},"reference-count":31,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2026,9,17]],"date-time":"2026-09-17T00:00:00Z","timestamp":1789603200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100004442","name":"National Science Centre","doi-asserted-by":"publisher","award":["DEC-2025\/09\/X\/ST8\/00288"],"award-info":[{"award-number":["DEC-2025\/09\/X\/ST8\/00288"]}],"id":[{"id":"10.13039\/501100004442","id-type":"DOI","asserted-by":"publisher"}]},{"award":["DEC-2025\/09\/X\/ST8\/00288"],"award-info":[{"award-number":["DEC-2025\/09\/X\/ST8\/00288"]}],"id":[{"id":"https:\/\/ror.org\/03ha2q922","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>Post-fire assessment of structural steel typically relies on residual mechanical properties, although thermally induced changes in deformation behaviour may emerge before conventional strength parameters are clearly affected. This study examines whether mechanically referenced acoustic emission (AE) descriptors can reveal such changes in S235 steel after exposure to 700, 900, and 1100 \u00b0C for 40, 80, and 120 min, followed by air cooling. Thirty specimens were subjected to tensile testing with two-channel AE monitoring. The two channels were recorded independently and were not combined. Channel 2 was used consistently for quantitative comparisons, whereas channel 1 served as a control of signal transmission and sensor coupling. Median cumulative AE counts were evaluated at 75% of the lower yield load, the lower yield point, ultimate tensile strength, and fracture. Thermal exposure altered both the magnitude and distribution of AE activity, with the greatest differences occurring before or near yielding. After exposure to 900 \u00b0C for 120 min, the mean lower yield strength decreased by approximately 14%, while pre-yield AE counts increased by approximately 210% relative to the reference condition. Specimens exposed to 1100 \u00b0C for 40 min showed similar final AE counts to the reference specimens but markedly different distributions across the loading stages. Stage-resolved AE analysis therefore provides information complementary to residual mechanical properties and final AE counts. Although the proposed pre-yield descriptor is retrospective and cannot be applied directly as a field-diagnostic threshold, it provides a sensitive experimental basis for comparing thermally modified deformation histories and for future development of independently defined AE-based assessment criteria.<\/jats:p>","DOI":"10.3390\/ma19183958","type":"journal-article","created":{"date-parts":[[2026,9,21]],"date-time":"2026-09-21T16:06:51Z","timestamp":1790006811000},"page":"3958","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Mechanically Referenced Early Acoustic Emission Indicators of Thermally Modified Deformation in S235 Structural Steel"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3314-3801","authenticated-orcid":false,"given":"Anna","family":"Adamczak-Bugno","sequence":"first","affiliation":[{"name":"Faculty of Civil Engineering and Architecture, Kielce University of Technology, Av. 1000-An. of Polish State 7, 25-314 Kielce, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,17]]},"reference":[{"key":"ref_1","unstructured":"(2024). Eurocode 3: Design of Steel Structures\u2014Part 1\u20132: Structural Fire Design (Standard No. EN 1993-1-2:2024)."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"237","DOI":"10.1002\/fam.849","article-title":"Mechanical Properties of Structural Steel at Elevated Temperatures and after Cooling Down","volume":"28","author":"Outinen","year":"2004","journal-title":"Fire Mater."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"423","DOI":"10.1061\/(ASCE)MT.1943-5533.0000041","article-title":"High-Temperature Properties of Steel for Fire Resistance Modeling of Structures","volume":"22","author":"Kodur","year":"2010","journal-title":"J. Mater. Civ. Eng."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"241","DOI":"10.1016\/j.tws.2014.06.010","article-title":"Experimental Investigation of Post-Fire Mechanical Properties of Cold-Formed Steels","volume":"84","author":"Gunalan","year":"2014","journal-title":"Thin Walled Struct."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1306","DOI":"10.1061\/(ASCE)MT.1943-5533.0000676","article-title":"Stress-Strain Curves of Structural and Reinforcing Steels after Exposure to Elevated Temperatures","volume":"25","author":"Tao","year":"2013","journal-title":"J. Mater. Civ. Eng."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"106651","DOI":"10.1016\/j.tws.2020.106651","article-title":"Experimental Investigation of Post-Fire Mechanical Properties of Q235 Cold-Formed Steel","volume":"150","author":"Ren","year":"2020","journal-title":"Thin Walled Struct."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"106767","DOI":"10.1016\/j.jcsr.2021.106767","article-title":"Post-Fire Mechanical Properties of Base Metal and Welds of Q235 Steel","volume":"183","author":"Shi","year":"2021","journal-title":"J. Constr. Steel Res."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"103848","DOI":"10.1016\/j.firesaf.2023.103848","article-title":"Heating Duration Effects on Post-Fire Structural Steel Mechanical Properties","volume":"140","author":"Gordon","year":"2023","journal-title":"Fire Saf. J."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"181","DOI":"10.1108\/JSFE-03-2017-0028","article-title":"Post-Fire Assessment and Reinstatement of Steel Structures","volume":"8","author":"Maraveas","year":"2017","journal-title":"J. Struct. Fire Eng."},{"key":"ref_10","unstructured":"Zhang, L.T., Liang, S.Y., An, W.Y., Wang, Y., Yang, Y., Duan, Y.J., and Qiao, J.C. (2026). A Stress-Rate-Driven Constitutive Framework for Rejuvenation in Metallic Glasses. Acta Mech. Sin."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"6877","DOI":"10.1038\/s41467-025-61707-z","article-title":"Detecting Deformation Mechanisms of Metals from Acoustic Emission Signals through Knowledge-Driven Unsupervised Learning","volume":"16","author":"Gou","year":"2025","journal-title":"Nat. Commun."},{"key":"ref_12","first-page":"177","article-title":"Acoustic Emission Produced by Deformation of Metals and Alloys\u2014A Review","volume":"6","author":"Heiple","year":"1987","journal-title":"J. Acoust. Emiss."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Mandal, D.D., Bentahar, M., El Mahi, A., Brouste, A., El Guerjouma, R., Montresor, S., and Cartiaux, F.-B. (2022). Acoustic Emission Monitoring of Progressive Damage of Reinforced Concrete T-Beams under Four-Point Bending. Mater., 15.","DOI":"10.3390\/ma15103486"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Sause, M.G.R., and Jasi\u016bnien\u0117, E. (2021). Acoustic Emission. Structural Health Monitoring Damage Detection Systems for Aerospace, Springer International Publishing. Springer Aerospace Technology.","DOI":"10.1007\/978-3-030-72192-3"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Ghadarah, N., and Ayre, D. (2023). A Review on Acoustic Emission Testing for Structural Health Monitoring of Polymer-Based Composites. Sensors, 23.","DOI":"10.3390\/s23156945"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1094","DOI":"10.1134\/S1063784208080203","article-title":"Acoustic Emission during the Development of a L\u00fcders Band in a Low-Carbon Steel","volume":"53","author":"Zuev","year":"2008","journal-title":"Tech. Phys."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"108367","DOI":"10.1016\/j.ijfatigue.2024.108367","article-title":"Detection of Early Fatigue Damage during Ultrasonic Fatigue Testing of Steel by Acoustic Emission Monitoring","volume":"185","author":"Seleznev","year":"2024","journal-title":"Int. J. Fatigue"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1016\/j.apacoust.2017.05.014","article-title":"Acoustic Emission Studies for Characterization of Fatigue Crack Growth in 316LN Stainless Steel and Welds","volume":"126","author":"Chai","year":"2017","journal-title":"Appl. Acoust."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"\u015awit, G., Dzioba, I., Adamczak-Bugno, A., and Krampikowska, A. (2022). Identification of the Fracture Process in Gas Pipeline Steel Based on the Analysis of AE Signals. Materials, 15.","DOI":"10.3390\/ma15072659"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"S108","DOI":"10.1002\/prs.12576","article-title":"Influence of High Temperature during Tensile Test for Stainless Steel Using Acoustic Emission","volume":"43","author":"Mohammad","year":"2024","journal-title":"Process Saf. Prog."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Adamczak-Bugno, A., Lipiec, S.M., and Adamczak, J. (2026). Evaluation of the Effect of Temperature (20\u2013700 \u00b0C) on the Properties of Prestressing Steel Using AE Signals and FEM Analysis. Materials, 19.","DOI":"10.3390\/ma19010023"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Adamczak-Bugno, A., Lipiec, S., Adamczak, J., Vi\u010dan, J., and Bahleda, F. (2023). Identification of Destruction Processes and Assessment of Deformations in Compressed Concrete Modified with Polypropylene Fibers Exposed to Fire Temperatures Using Acoustic Emission Signal Analysis, Numerical Analysis, and Digital Image Correlation. Materials, 16.","DOI":"10.3390\/ma16206786"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Adamczak-Bugno, A., \u015awit, G., Krampikowska, A., and Proverbio, E. (2022). Analysis of the Significance of Changes in the Number and Energy Parameters of Acoustic Emission Signals on the Assessment of the Strength of Fibre\u2013Cement Boards. Materials, 15.","DOI":"10.3390\/ma15165757"},{"key":"ref_24","unstructured":"(2019). Hot Rolled Products of Structural Steels\u2014Part 2: Technical Delivery Conditions for Non-Alloy Structural Steels (Standard No. EN 10025-2)."},{"key":"ref_25","unstructured":"(2019). Metallic Materials\u2014Tensile Testing\u2014Part 1: Method of Test at Room Temperature (Standard No. PN-EN ISO 6892-1:2019)."},{"key":"ref_26","unstructured":"(2018). Metallic Materials\u2014Calibration and Verification of Static Uniaxial Testing Machines\u2014Part 1: Tension\/Compression Testing Machines\u2014Calibration and Verification of the Force-Measuring System (Standard No. ISO 7500-1:2018)."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"MISTRAS Group (2026). Express-8\u2014PCI Express-Based Eight-Channel AE Board & System, MISTRAS Group.","DOI":"10.1088\/2631-8695\/ae9675"},{"key":"ref_28","unstructured":"Vallen Systeme GmbH (2026, September 11). VS75-SIC-40dB Acoustic Emission Sensor. Available online: https:\/\/www.vallen.de\/sensors\/low-frequency-sensors-30-100-khz\/vs75-sic-40db\/."},{"key":"ref_29","unstructured":"(2026). Standard Guide for Determining the Reproducibility of Acoustic Emission Sensor Response (Standard No. ASTM E976-15(2026))."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"102576","DOI":"10.1016\/j.coco.2025.102576","article-title":"Superior Creep Resistance of Multiscale Architectural Titanium Matrix Composites: Insights from Microscale Internal Stress","volume":"59","author":"Chen","year":"2025","journal-title":"Compos. Commun."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Ozevin, D., and Kessler, S. (2022). The Dependence of Acoustic Emission Behavior on Prior Fatigue Loading History. Front. Built Environ., 8.","DOI":"10.3389\/fbuil.2022.981327"}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/19\/18\/3958\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,21]],"date-time":"2026-09-21T16:09:21Z","timestamp":1790006961000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/19\/18\/3958"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,17]]},"references-count":31,"journal-issue":{"issue":"18","published-online":{"date-parts":[[2026,9]]}},"alternative-id":["ma19183958"],"URL":"https:\/\/doi.org\/10.3390\/ma19183958","relation":{},"ISSN":["1996-1944"],"issn-type":[{"value":"1996-1944","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,17]]}}}